Disk cartridge

ABSTRACT

A disk cartridge is provided which includes a cartridge body ( 2 ) including a lower shell ( 6 ) having formed therein a first opening ( 24 ) for write and/read and an upper shell ( 7 ) butt-joined to the lower shell ( 6 ), a rotation wheel ( 4 ) housed rotatably in the cartridge body ( 2 ) and which houses a disk ( 3 ) and has formed therein a second opening ( 44 ) corresponding to the fist opening ( 24 ) and through which the housed disk ( 3 ) is exposed to outside, a pair of shutter plates ( 5   a,    5   b ) provided between the lower shell ( 7 ) and rotation wheel ( 4 ) and which operates with the rotation of the rotation wheel ( 4 ) to uncover the first and second openings ( 24, 44 ) when the latter are coincide with each other, and a locking mechanism ( 71 ) including a locking portion ( 76 ) installed pivotably to the upper shell ( 6 ) and engaged in an engagement concavity ( 85 ) in the rotation wheel ( 4 ) to lock the rotation wheel ( 4 ) in a position where the pair of shutter plates ( 5   a,    5   b ) covers the first opening ( 14 ), and an unlocking portion ( 77 ) which cancels the engagement of the locking portion ( 76 ) in the engagement concavity ( 85 ).

TECHNICAL FIELD

The present invention generally relates to a disk cartridge in which adisk used as a recording medium is housed, and more particularly to adisk cartridge including a locking mechanism which locks a shutter,which uncovers and covers an opening through which a part of a disk isexposed to outside, in a position to cover the opening.

This application claims the priority of the Japanese Patent ApplicationNo. 2003-305311, filed on Aug. 28, 2003, the entirety of which isincorporated by reference herein.

BACKGROUND ART

A disk cartridge is disclosed in the Japanese Patent Application LaidOpen No. 2003-109343. This disk cartridge includes a cartridge bodyincorporating an inner rotor and shutter mechanism. The inner rotorhouses an optical disk. The inner rotor rotates inside the cartridgebody. When an opening formed in the inner rotor coincides with anopening formed in the cartridge body, the optical disk housed in theinner rotor is exposed to outside.

Note here that an optical disk used as a recording medium in the diskcartridge has information signals recorded at a high density. Dust orlike, if any, adhering to the optical disk will make it impossible torecord information signals accurately to the optical disk. On thisaccount, to keep the opening from being uncovered while the diskcartridge is not in use, a locking member is provided to keep the innerrotor from rotating. The locking member includes a locking portionprovided pivotably inside the cartridge body to be engaged in aconcavity formed in the periphery of the inner rotor, and ato-be-operated portion which cancels the engagement of the lockingportion in the concavity when the disk cartridge is located into a diskrecorder and/or player.

In the locking member, the engagement of the locking portion in theconcavity is canceled if the inner rotor is forcibly rotated while thedisk cartridge is not in use. If the locking portion of the lockingmember is disengaged from the concavity in the inner rotor, inner rotoris rotated and thus the optical disk is exposed to outside, dust or thelike will possibly adhere to he surface of the optical disk, therebymaking it impossible to positively write or read information signals toor from the optical disk.

DISCLOSURE OF THE INVENTION

Accordingly, the present invention has an object to overcome theabove-mentioned drawbacks of the conventional disk cartridge.

The present invention has another object to provide a disk cartridgeincluding a shutter mechanism configured to positively be locked and notto forcibly be unlocked even if it is tried.

The present invention has still another object to provide a diskcartridge including a locking mechanism which prevents further invasionof dust or the like beyond it.

The present invention has yet another object to provide a disk cartridgeincluding a shutter which can easily be unlocked during a series ofoperations for insertion of the disk cartridge into a disk recorderand/or player.

The above object can be attained by providing a disk cartridgeincluding, according to the present invention, a cartridge bodyincluding a lower shell having formed therein a first opening for writeand/read and an upper shell butt-joined to the lower shell; a rotationwheel housed rotatably in the cartridge body and which houses a disk andhas formed therein a second opening corresponding to the fist openingand through which the housed disk is exposed to outside; and a shuttermechanism provided between the lower shell and rotation wheel and whichoperates with the rotation of the rotation wheel to uncover the firstand second openings when the latter are coincide with each other; and alocking mechanism including a shaft portion installed pivotably to anyone of the shells, a locking portion engaged in an engagement concavityin the rotation wheel to lock the rotation wheel in a position where theshutter mechanism covers the first opening, and an unlocking portionwhich cancels the engagement of the locking portion in the engagementconcavity. The cartridge body has formed therein an insertion guiderecess open at the side of the cartridge body, at which the latter isfirst inserted into a disk recorder and/or player. The locking portionhas an unlocking piece which is exposed in the insertion guide recess.

In the disk cartridge according to the present invention, the shuttermechanism can be unlocked by an insertion guide means included in thedisk recorder and/or player. Thus, the locking mechanism can besimplified and provide more positive locking while the disk cartridge isnot in use.

These objects and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription of the best mode for carrying out the present invention whentaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view, from the upper shell, of the diskcartridge according to the present invention.

FIG. 2 is a perspective view, from the lower shell, of the diskcartridge according to the present invention.

FIG. 3 is an exploded perspective view of the disk cartridge accordingto the present invention.

FIG. 4 is a plan view, from inside the upper shell, of the diskcartridge.

FIG. 5 is a perspective view of the substantial portion, at the frontside, of the upper shell.

FIG. 6 is a plan view, from inside the lower shell, of the diskcartridge.

FIG. 7 is a plan view of the substantial portion, explaining therelation between an insertion guide recess and insertion guide pin.

FIG. 8 is a perspective view, from the side at which an optical disk isto be inserted, of the rotation wheel.

FIG. 9 is a perspective view, from the surface of the rotation wheel, ofthe lower shell.

FIG. 10 is a perspective view of the substantial portion, explaining ato-be-operated member formed on the rotation wheel.

FIG. 11 is a perspective view of the substantial portion, explaining amechanism for preventing the shutter plate from going up.

FIG. 12 is a sectional view of the substantial portion, explaining anengagement projection of a forcing member which forces the rotationwheel in one direction.

FIG. 13 is a perspective view of the shutter plates and rotation wheel.

FIG. 14 is a sectional view of the substantial portion, showing apivoting support mechanism for the first shutter plate.

FIG. 15 is a sectional view of the substantial portion, showing a guidemechanism for the first shutter plate.

FIG. 16 is a sectional view of the substantial portion, showing apivoting support mechanism for the second shutter plate.

FIG. 17 is a plan view of the shutter plates covering the write and/orread opening, with the lower shell and optical disk being omitted.

FIG. 18 is a plan view of the shutter plates uncovering the write and/orread opening, with the lower shell and optical disk being omitted.

FIG. 19 is an exploded perspective view of a locking mechanism.

FIG. 20 is a sectional view of the substantial portion of the rotationwheel, showing the relation between a taper portion of the rotationwheel and locking recess.

FIG. 21 is a sectional view of the substantial portion, showing theinsertion guide recess to which an unlocking piece is opposite and inwhich an unlocking pin is not inserted.

FIG. 22 is a sectional view of the substantial portion, showing theinsertion guide recess in which the unlocking pin is inserted.

FIG. 23 is a front view of the substantial portion, showing the relationbetween the width of the insertion guide recess and thickness of theunlocking pin.

FIG. 24 is a plan view showing the relation among the insertion guiderecess, location hole and alignment hole.

FIG. 25 is a perspective view of the disk cartridge with the firstopening being uncovered.

BEST MODE FOR CARRYING OUT THE INVENTION

The disk cartridge according to the present invention will be describedbelow with reference to the accompanying drawings. The disk cartridgeaccording to the present invention is still compatible with, and canthus be loaded into, a disk recorder and/or player in which the diskcartridge having the standard size as that disclosed in theaforementioned Japanese Patent Application Laid Open No. 2003-109343.

The disk cartridge having the standard size, as disclosed in the aboveJapanese Unexamined Patent Application Publication, houses an opticaldisk whose diameter is about 12 cm. The disk cartridge according to thepresent invention houses an optical disk whose diameter is smaller thanthat of the optical disk encased in the standard-sized disk cartridge.Being smaller in diameter than the optical disk in the standard-sizeddisk cartridge, the optical disk encased in the disk cartridge accordingto the present invention is smaller in recording capacity than theoptical disk in the standard-sized disk cartridge but the disk cartridgeaccording to the present invention has a smaller contour and thus moreexcellent in portability than the standard-sized disk cartridge.

As shown in FIGS. 1 to 3, the disk cartridge according to the presentinvention, generally indicated with a reference numeral 1, includes acartridge body 2. The cartridge body 2 incorporates a rotation wheel 4in which an optical disk 3 is housed, and a pair of first and secondshutter plates 5 a and 5 b forming together a shutter mechanism. Thecartridge body 2 is formed from a pair of upper and lower shells 6 and 7butt-joined to each other.

The optical disk 3 used in the disk cartridge 1 according to the presentinvention has formed in the center thereof a center hole 3 a in which adisk rotation driving mechanism of the disk recorder and/or player is tobe engaged. The optical disk 3 used in the present invention may be aread-only optical disk formed from a substrate having pre-formed thereona bit pattern corresponding to information signals, a rewritable opticaldisk whose recording layer is formed from a phase-change material or arecordable optical disk whose recording layer is formed from an organicdye or the like. Further, according to the present invention, therecording medium may not only be an optical disk but also amagneto-optical disk, magnetic disk or the like.

As shown in FIG. 4, the upper shell 6 of the cartridge body 2 is formedby injection molding of a synthetic resin using a molding machine. Theupper shell 6 is formed to have a generally rectangular plane and agenerally circular front end at which the disk cartridge 1 is firstintroduced into the disk recorder and/or player. Further, the uppershell 6 has a peripheral wall 8 forming the lateral side of thecartridge body 2. The peripheral wall 8 is upright along the peripheraledge of the main surface of the upper shell 6.

In addition, the peripheral wall 8 has formed in the central portion ofthe front side thereof a first pickup admission concavity 9 forintroduction of an optical pickup of the disk recorder and/or playerinto the disk cartridge 1. Also, the peripheral wall 8 has formed, forexample, at each corner thereof a boss 10 having formed therein a screwhole for joining the upper shell 6 to the lower shell 7.

Inside the peripheral wall 8, a generally circular inner wall 11 insidewhich the rotation wheel 4 is placed is formed to inscribe theperipheral wall 8 as shown in FIG. 5. The inner wall 11 is to house therotation wheel 4 rotatably. The inner wall 11 has formed in the centralportion of the front side a second pickup admission concavity 12 forintroduction of the optical pickup of the disk recorder and/or player.The inner wall 11 houses the rotation wheel 4 rotatably and guides thelatter being rotated. When the rotation wheel 4 is housed as above, themain surface of the upper shell 6 defines a disk compartment along withthe rotation wheel 4. Also, a lifter 14 to lift the rotation wheel 4 isformed at the inner base of the inner wall 11 and near the second pickupadmission concavity 12. The lifter 14 lifts the rotation wheel 4 towardthe lower shell 7 when the first and second shutter plates 5 a and 5 bcover together a first opening 24.

Nearly at a generally central portion of the inner surface of the uppershell 6, there is installed a clamping plate 13 which holds the opticaldisk 3 along with a disk table provided in the disk rotation drive ofthe disk recorder and/or player. The clamping plate 13 is installed witha fixing ring 13 a. More specifically, being held between the fixingring 13 a and the nearly central portion of the inner surface of theupper shell 6, the clamping plate 13 is fixed to the nearly centralportion of the inner surface of the upper shell 6 by welding orotherwise securing the fixing ring 13 a. A centering piece provided atthe center of the disk table is engaged in the center hole 3 a in theoptical disk 3, and the optical disk 3 is held between the disk tableand clamping plate 13 to be rotatable inside the disk compartment.

Note that on the inner surface of the upper surface 6, there are furtherformed a rising wall 16 a forming a location hole 26 a in the lowershell 7 and a rising wall 16 b forming an alignment hole 26 b.

The lower shell 7 which is to joined to the upper shell 6 constructed asabove is formed by injection molding of a synthetic resin by means ofthe molding machine like the upper shell 6, as shown in FIGS. 2, 3 and6. The lower shell 7 has a main surface which is generally rectangular.Of this main surface, a front-side portion is formed generally circular.The disk cartridge 1 is to be inserted first at this front-side portionthereof into the disk recorder and/or player. The lower shell 7 has aperipheral wall 21 extending upright along the peripheral edge of themain surface of the lower shell 7 and which forms the lateral side ofthe cartridge body 2, and an inner wall 28 formed to inscribe theperipheral wall 21.

The lower shell 7 has formed in the central portion of the front side ofthe peripheral wall 21 a first opening 24 through which the opticalpickup and disk table are introduced. The first opening 24 includes agenerally rectangular optical pickup admission opening 24 a extendingfrom the open end of the front side of the lower shell 7 and throughwhich the signal recording surface of the optical disk 3 is partiallyexposed in a range between the inner and outer radii of the optical disk3, and a rotation driving opening 24 b contiguous to the optical pickupadmission opening 24 a and through which the center hole 3 a of theoptical disk 3 is exposed to outside. That is, the write/read opening(optical pickup admission opening) 24 a has a sufficient size tointroduce the optical pickup of the disk recorder and/or player into thecartridge body 2, and also the rotation driving opening 24 b has asufficient size to introduce the disk table provided in the diskrotation driving mechanism of the disk recorder and/or player into thecartridge body 2. Further, at one opening end of the optical pickupadmission opening 24 a, there is formed a taper portion 24 c incliningin a direction of increasing the width of the opening end. The taperportion 24 c is to house a to-be-operated member 45 of the rotationwheel 4, which is in a position for the first and second shutter plates5 a and 5 b to uncover the first opening 24. The to-be-operated member45 will be described in detail later.

At each of the lateral edges of the write/read opening 24 a and rotationdriving opening 24 b, both forming the first opening 24, there is formeda projection 27 which prevents dust or the like from invading thecartridge body 2 when the pair of first and second shutter plates 5 aand 5 b is covering the first opening 24.

Also, on the rear side of the peripheral wall 21, there are formedbosses 22 corresponding to the aforementioned bosses 10 formed on theupper shell 6. Each of the bosses 10 has the screw hole formed thereinas mentioned above, and also each of the bosses 22 has formed therein athrough-hole where are to be aligned with the corresponding one of thescrew holes in the bosses 10 when the upper and lower shells 6 and 7 arebutt-joined to each other. As shown in FIG. 2, the upper and lowershells 6 and 7 are joined to each other with screws 23 passed throughthe through-holes in the bosses 22 on the lower shell 7 and driven intothe screw holes in the bosses 10 on the upper shell 6.

Further, on the front side of the lower shell 7, there are formedinsertion guide recesses 25 a and 25 b in which insertion guide membersof the disk recorder and/or player are engaged when the disk cartridge 1is inserted into the disk recorder and/or player. The insertion guiderecesses 25 a and 25 b are formed widest at the opening ends thereof foreasier introduction of insertion guide pins 100 as shown in FIG. 7. Itshould be noted that the innermost portion of each of the insertionguide recesses 25 a and 25 b may be formed to have a width nearly equalto the outside diameter of the insertion guide pin 100. Thus, whenplaced on the cartridge mount in the disk recorder and/or player, thedisk cartridge 1 can be positioned plane-directionally to preventbacklash. Also, there is provided a locking mechanism 71 in a positionnear one (25 b) of the insertion guide recesses as will be described indetail later. The locking mechanism 71 includes a locking member 72. Anunlocking piece 77 of the locking member 72 is engaged in the insertionguide recess 25 a. The insertion guide pin 100 engaged in the insertionguide recess 25 b works as an unlocking pin which will press theunlocking piece 77.

Moreover, near one of the corners at the rear side of the lower shell 7,there is formed the location hole 26 a which is a reference hole forpositioning and loading the disk cartridge 1 in the disk recorder and/orplayer, as shown in FIGS. 2 and 6. Also, the adjusting alignment hole 26b is formed near the other corner.

Note that on both lateral sides of the cartridge body 2 formed from theupper and lower shells 6 and 7 butt-joined to each other, parallel tothe direction of introduction into the disk recorder and/or player,there are formed guide recesses 15 extending from the front to rear end,as shown in FIGS. 1 and 2. The guide recesses 15 guide the diskcartridge 1 being introduced into the disk recorder and/or player.

The upper and lower shells 6 and 7, when butt-joined to each other,define together inside the inner wall 11 a compartment for housing therotation wheel 4. The rotation wheel 4 housed in the compartment isformed by injection molding of a synthetic resin by means of a moldingmachine as shown in FIGS. 8 and 9. The rotation wheel 4 has a generallydish-like main surface. With the rotation wheel 4 being placed at theconvex side thereof in the cartridge body 2, the upper shell 6 and themain surface of one of the first and second shutter plates 5 a and 5 bdefine together a disk compartment. The rotation wheel 4 is formedgenerally circular to have an annular projection 43 being upright alongthe peripheral edge thereof. The rotation wheel 4 has formed in the mainsurface thereof a second opening 44 nearly equal in size to the firstopening 24 formed in the lower shell 7.

When the second opening 44 coincides with the first opening 24 in thelower shell 7, the optical disk 3 housed in the rotation wheel 4 isexposed to outside. More particularly, the second opening 44 includes anopening corresponding to the optical pickup admission opening 24 a ofthe first opening 24 and an opening corresponding to the rotationdriving opening 24 b. Also, the second opening 44 is formed to begradually wider from the center toward the periphery in order toaccommodate a difference from the first opening 24 and prevent the firstopening 24 from being narrowed due to any working error or installationerror of the rotation wheel 4. For example, the second opening 44 isformed to have both the radial edges inclined about 1 deg. outward.

Also, along the base end of the annular projection 43, there is formed ataper portion 42 inclined toward the main surface of the rotation wheel4 as shown in FIG. 8. The taper portion 42 supports the peripheral edgeof the optical disk 3 by line contact to prevent the signal recordingsurface of the optical disk 3 from being scratched by plane contact withthe main surface of the rotation wheel 4.

Also, outside the second opening 44, there are provided the pair offirst and second shutter plates 5 a and 5 b as shown in FIG. 2. On thisaccount, taper portions 44 a and 44 b are formed on the opposite lateraledges of the second opening 44, as shown in FIG. 9, to prevent the firstand second shutter plates 5 a and 5 b from entering the second opening44. Further, the rotation wheel 4 has formed thereon an engagementrecess 50 in which the first shutter plate 5 a is engaged when the firstand second shutter plates 5 a and 5 b cover the first and secondopenings 24 and 44. The shutter plate 5 a is thus prevented from goingup. The engagement recess 50 is defined by a piece formed to have agenerally L-shaped section and whose opening end is the lateral edge ofthe first opening 24.

As shown in FIG. 10, near the second opening 44 in the rotation wheel 4,there is formed the to-be-operated member 45 projected to outside and inwhich there is engaged a shutter releasing pin 41 provided in a shutterreleasing mechanism of the disk recorder and/or player. Theto-be-operated member 45 includes a first piece 45 a and second piece 45b. The first and second to-be-operated pieces 45 a and 45 b formtogether a concavity in which the shutter pin releasing pin 41 of thedisk recorder and/or player is to be engaged. When the rotation wheel 4is rotated in a direction in which the first and second shutter plates 5a and 5 b will uncover the first and second openings 24 and 44, theshutter releasing pin 41 will abut the first to-be-operated piece 45 a.When the rotation wheel 4 is rotated in a direction in which the firstand second shutter plates 5 a and 5 b will cover the first and secondopenings 24 and 44, the shutter releasing pin 41 will abut the secondto-be-operated piece 45 b. As will further be described later, therotation wheel 4 is forced by a forcing member 48 to rotate in thedirection of arrow A in FIG. 10 in which the shutter plates 5 a and 5 bwill uncover the first and second openings 24 and 44, and thus the firstto-be-operated piece 45 a is applied with a force larger than a forceapplied to the second to-be-operated piece 45 b. On this account, thefirst to-be-operated piece 45 a is formed larger than the secondto-be-operated piece 45 b to have a larger mechanical strength. Morespecifically, the first to-be-operated piece 45 a is formed to have aheight h₁ which is larger than a height h₂ of the second to-be-operatedpiece 45 b. Thus, the first to-be-operated piece 45 a has a largermechanical strength for more positive engagement of the shutterreleasing pin 41.

As the rotation wheel 4 is rotated, the to-be-operated member 45constructed as above is exposed to outside from the front side of thelower shell 7 in which the first opening 24 is formed, and moved in thedirection of the width of the first opening 24. The to-be-operatedmember 45 stays at the portion widened by the taper portion 24 c whenthe shutter plates 5 a and 5 b are uncovering the first opening 24.

As shown in FIG. 11, the to-be-operated member 45 has also an engagementrecess 45 c formed at the base ends of the first and secondto-be-operated pieces 45 a and 45 b and in which the first shutter plate5 a is engaged. While the shutter plates 5 a and 5 b are covering thefirst and second openings 24 and 44, the first shutter plate 5 a isengaged in the engagement recess 45 c to prevent the latter from goingup or down. Therefore, there arises no clearance between the peripheraledge of the first opening 24 and the first shutter plate 5 a, and thusit is possible to prevent dust or the like from invading the cartridgebody 2. That is, the engagement recess 45 c formed in the to-be-operatedmember 45 is cooperative with the engagement recess 50 formed near thesecond opening 44 in the rotation wheel 4 to prevent the first shutterplate 5 a from going up or down. Therefore, there arises no clearancebetween the second opening 44 and shutter plate 5 a and thus it ispossible to prevent dust or the like from invading the cartridge body 2.

Note that the second to-be-operated piece 45 b abuts a limiter 29coupling the peripheral wall 8 and inner wall 11 of the upper shell 6,opposite to a part of the peripheral edge of the first opening 24 in thelower shell 7, to define a pivoting range of the rotation wheel 4.

Also, the pair of shutter plates 5 a and 5 b is disposed between therotation wheel 4 and lower shell 7. To reduce the area of contact withthe shutter plates 5 a and 5 b, and thus the sliding resistance, aplurality of projections 46 is formed on the surface of the rotationwheel 4 on which the shutter plates 5 a and 5 b are disposed, as shownin FIG. 9. The projection 46 is formed circular to have a height ofabout 20 μm.

The rotation wheel 4 constructed as above is forced by a forcing member48 such as a helical spring or the like to rotate in a direction inwhich the shutter plates 5 a and 5 b will cover the first and secondopenings 24 and 44. The forcing member 48 is hooked at one end thereofon a retention piece 48 a formed on the annular projection 43 of therotation wheel 4 and at the other end on an retention projection 48 bformed on the inner surface of the upper shell 6 as shown in FIG. 4. Asthe rotation wheel 4 is rotated, the forcing member 48 expands andcontracts. Inside the inner wall 11, there is formed a rising wall onthe inner surface of the upper shell 6. Between the rising wall andperipheral wall 8, there is defined a guide recess 49 which guides theforcing member 48 which will thus gently expand and contract inside thecartridge body 2. Also, along the peripheral edge of the rotation wheel4, there is formed a flange 47 which closes almost entirely the guiderecess 49 as shown in FIGS. 8 and 9.

Note that as shown in FIG. 12, the retention projection 48 b formed onthe inner surface of the upper shell 6 is engaged at the free endthereof on a generally cylindrical reinforcing rib 48 c formed on theinner surface of the lower shell 7 to reinforce the retention projection48 b which will be applied with the force of the forcing member 48 whenthe upper and lower shells 6 and 8 are joined to each other.

The rotation wheel 4 constructed as above is forced by the forcingmember 48 such as a helical spring or the like to rotate in a directionin which the shutter plates 5 a and 5 b will cover the first and secondopenings 24 and 44, and thus the to-be-operated member 45 is rotated bythe shutter releasing pin 41 at the disk recorder and/or player in adirection in which the shutter plates 5 a and 5 b will uncover the firstand second openings 24 and 44. At this time, the inner wall 11 willguide the rotation wheel 4 being rotated.

Of the shutter plates 5 a and 5 b in pair provided in the shuttermechanism to uncover and cover the first opening 24 in the lower shell 7and second opening 44 in the rotation wheel 4, the first one (plate 5 a)is formed larger than the second one (5 b) as shown in FIG. 13.

As shown in FIG. 13, the first shutter plate 5 a includes a firstshutter portion 51 which covers the first and second openings 24 and 44,a first pivoting support portion 53 supported pivotably on a first shaft52 formed on the inner surface of the upper shell 6 and between theperipheral wall 8 and inner wall 11, and a second shaft hole 54 at whichthe smaller shutter plate 5 b is coupled to the first shutter plate 5 a.

The first shutter portion 51 includes a first lateral edge 51 apositioned at one lateral edge of the second opening 44 in the rotationwheel 4 when the second opening 44 is covered, a second lateral edge 51b contiguous to the first lateral edge 51 a and a third lateral edge 51c contiguous to the second lateral edge 5 b. The second lateral edge 51b is formed to bend inwardly of the first lateral edge 51 a, and thethird lateral edge 5 c is formed to bend outwardly of the second lateraledge 51 b. Further, the first shutter portion 51 includes a fourthlateral edge 51 d formed opposite to the first to third lateral edges 51a to 51 c. The fourth lateral edge 51 d has formed therein a wavelikeclearance cut 51 e which keeps the first shutter portion 51 off thebosses 10 and 22, location holes 26 a, write-protection member, etc.formed at one corner of the upper and lower shells 6 and 7,respectively. The second and third lateral edges 51 b and 51 c aretapered in opposite directions, respectively. Also, the first lateraledge 51 a is engaged in the engagement hole 50 in the rotation wheel 4and thus the first shutter plate 5 a is prevented from going up.

Further, on the side of the first shutter portion 51, opposite to thelower shell 7, there is formed a recess 51 f in which the projection 27formed on the peripheral edge of the first opening 24 in the lower shell7 is engaged. When the rotation wheel 4 is lifted by the lifter 14 onthe upper shell 6 to the lower shell 7 while the shutter plates 5 a and5 b are covering the first and second openings 24 and 44, the projection27 formed on the peripheral edge of the first opening 24 is engaged inthe recess 51 f, whereby dust or the like is prevented from invading thecartridge body 2.

Moreover, on the side of the first shutter portion 51, opposite to theoptical disk 3, there is formed a guide projection 51 g which is to beengaged in a guide recess 55 formed in the main surface of the rotationwheel 4. Being engaged in the guide recess 55, the guide projection 51 glimits pivoting of the first shutter plate 5 a. In addition, on the sideof the first shutter portion 51, opposite to the optical disk 3, thereis formed a limiting projection 51 h which retrains the shutter plate 5a from being displaced. The limiting projection 51 h is thus formed in aposition corresponding to an inner radius-side area, not for recordingsignals, around the center hole 3 a in the optical disk 3, and preventsthe signal recording surface of the optical disk 3 from being scratchedby the first shutter plate 5 a accidentally pressed and displacedinwardly while the shutter plates 5 a and 5 b are covering the first andsecond openings 24 and 44. While the shutter plates 5 a and 5 b areuncovering the first and second openings 24 and 44, the limitingprojection 51 h enters an undercut 56 formed near the center in therotation wheel 4 and will not limit pivoting of the shutter plate 5 a.

The first pivoting support portion 53 of the shutter plate 5 a is formedthicker than the shutter portion 51 to be more rigid, and has formedtherein a first shaft hole 53 a through which the first shaft 52 formedon the upper shell 6 is passed. As shown in FIG. 14, the first shaft 52is formed to have such a height that it will project from the firstpivoting support portion 53 when it is passed through the first shafthole 53 a. The free end of the first shaft 52 is engaged in a bearingportion 57 formed on the lower shell 7 to prevent the first pivotingsupport portion 53 from being disengaged from the first shaft 52 even ifthe disk cartridge is applied with an impact or shock when dropped, andreinforces the first shaft 52.

As shown in FIG. 13, the second shutter plate 5 b engaged on the firstshutter plate 5 a constructed as above includes a second shutter portion61 which covers the first and second openings 24 and 44 along with thefirst shutter portion 51, and a second pivoting support portion 62installed in the second shaft hole 54 formed in the first shutter plate5 a.

The second shutter portion 61 includes a first lateral edge 61 a whichengages on the second lateral edge 51 b of the first shutter portion 51,a second lateral edge 61 b contiguous to the first lateral edge 61 a andwhich engages on the third lateral edge 51 c of the first shutterportion 51, and a third lateral edge 61 c formed at the other side ofthe second lateral edge 61 b and contiguous to the first lateral edge 61a. The first lateral edge 61 a is tapered in a direction opposite to thetapering of the second lateral edge 51 b of the first shutter portion51, and the second lateral edge 61 b is tapered in a direction oppositeto the tapering of the third lateral edge 51 c of the first shutterportion 51. In addition, the first and second lateral edges 61 a and 61b are also tapered in opposite directions. When the shutter plates 5 aand 5 b cover the first and second openings 24 and 44, the secondlateral edge 61 b of the first shutter portion 51 is put into mesh withthe taper portion of the first lateral edge 61 a of the second shutterportion 61 in one direction while the taper portion of the third lateraledge 51 c of the first shutter portion 51 is in mesh with the taperportion of the second lateral edge 61 b of the second shutter portion 61in a direction opposite to the above one direction. Therefore, while thepair of shutter plates 5 a and 5 b is covering the first and secondopenings 24 and 44, they are in mesh with each other to prevent dust orthe like from invading the cartridge body 2 from the abutment betweenthem and they are thus not easy to be flexed when pressed.

Also, while the shutter plates 5 a and 5 b are covering the first andsecond openings 24 and 44, the first shutter plate 5 a is engaged in theengagement recess 45 c of the to-be-operated member 45 formed on therotation wheel 4 and the first lateral edge 51 a of the first shutterportion 51 is engaged in the engagement recess 50, thereby preventingthe first shutter plate 5 a from going up or down. Therefore, there willarise no clearance between the lateral edge of the first opening 24 andthe first shutter plate 5 a, and hence dust or the like will beprevented from invading the cartridge body 2.

Further, a projection 61 d is formed at the end of the third lateraledge 61 c opposite to the first lateral edge 61 a. When the secondshutter plate 5 b is covering the first and second openings 24 and 44,the projection 61 d is engaged in an engagement recess 61 e formed nearthe first opening 24 at the front side of the lower shell 7 to preventdust or the like from invading the cartridge body 2 from a clearancebetween the first opening 24 and second shutter plate 5 b.

Moreover, the second shutter portion 61 has formed thereon a firstrecess-shaped cam portion 64 in which there is engaged a first controlprojection 63 formed on the rotation wheel 4. When the first controlprojection 63 is engaged in the first cam portion 64, the lattercontrols the pivoting of the second shutter plate 5 b. The first camportion 64 includes a narrow portion 64 a formed at the peripheral sideof the rotation wheel 4, and a wide portion 64 b formed near the centerof the rotation wheel 4 and larger than the narrow portion 64 a. Thenarrow portion 64 a pivots the second shutter plate 5 b in a former halfof a pivoting stroke of the second shutter plate 5 b uncovering thefirst and second openings 24 and 44. When the first control projection63 moves to the wide portion 64 b, the force of pivoting is removed fromthe second shutter plate 5 b.

Note that the free end of the first control projection 63 formed on therotation wheel 4 is engaged in the relief recess 63 a formed in theinner surface of the lower shell 7 as shown in FIG. 15, therebypreventing the first control projection 63 from being disengaged fromthe first cam portion 64 due to a shock or the like.

Also, the second shutter portion 61 has formed thereon a second controlprojection 66 which is engaged in a second recess-shaped cam portion 65formed in the main surface of the rotation wheel 4. The second camportion 65 includes a first bent portion 65 a bent at the center of therotation wheel 4 in a first direction, and a second bent portion 65 bbent at the periphery of the rotation wheel 4 in a second directionopposite to the bent direction of the first bent portion 65 a. The firstbent portion 65 a will not act in any way in the former half of thepivoting stoke of the second shutter plate 5 b uncovering the first andsecond openings 24 and 44. However, when the second control projection66 moves to the second bent portion 65 b, namely, in the latter half ofthe pivoting stroke of the second shutter plate 5 b, the second bentportion 65 b pivots the second shutter plate 5 b on behalf of theaforementioned first cam portion 64.

The second pivoting support portion 62 has a second shaft 62 a formedthereon. The second shaft 52 a is passed through a second shaft hole 54formed in the first pivoting support portion 53 of the first shutterplate 5 a. Therefore, the second shutter plate 5 b is pivoted not inrelation to the rotation wheel 4 but in relation to the first shutterplate 5 a. It should be noted that as shown in FIG. 16, the free end ofthe second shaft 62 a projects from the second pivoting support portion62 and is engaged in the relief recess 62 b formed in the inner surfaceof the lower shell 7, thereby preventing the second shaft 62 a frombeing disengaged from the second shaft hole 54 due to a shock or thelike.

Next, the rotation of the rotation wheel 4 and operation of the firstand second shutter plates 5 a and 5 b will be described with referenceto FIGS. 17 and 18. FIG. 17 shows the first and second shutter plates 5a and 5 b covering the first and second openings 24 and 44. While thefirst and second shutter plates 5 a and 5 b are covering the first andsecond openings 24 and 44, the rotation wheel 4 is forced by the forcingmember 48 to rotate in the direction of arrow A in FIG. 17 and theto-be-operated member 45 is positioned at one lateral edge of the firstopening 24. The second lateral edge 51 b of the first shutter portion 51and the taper portion of the first lateral edge 61 a of the secondshutter portion 61 are in mesh with each other in one direction and thetaper portion of the third lateral edge 51 c of the first shutterportion 51 and that of the second lateral edge 61 b of the secondshutter portion 61 are in mesh with each other in a direction oppositeto the one direction, thereby preventing dust or the like from invadingthe cartridge body 2 from the abutment between the shutter plates 5 aand 5 b and the shutter plates 5 a and 5 b from being easily flexed whenpressed.

At this time, the guide projection 51 g of the first shutter plate 5 astays at one end of the guide recess 55 in the rotation wheel 4, nearthe center of the latter. Also, the first control projection 63 isengaged in the narrow portion 64 a of the first cam portion 64 of thesecond shutter plate 5 b. Further, the second control projection 66 ofthe second shutter plate 5 b is engaged in the first bent portion 65 aof the second cam portion 65 of the rotation wheel 4.

When the rotation wheel 4 is rotated by the to-be-operated member 45against the force of the forcing member 48 in a direction opposite tothe direction of arrow A in FIG. 17, the first shutter plate 5 a havingthe guide projection 51 g thereof engaged in the guide recess 55 isrotated about the first shaft 52 on the upper shell 6 in the directionof arrow B in FIG. 17. As the first shutter plate 5 a is pivoted, thesecond shutter plate 5 b will be pivoted about the second shaft 62 a ofthe first shutter plate 5 a in the direction of arrow C in relation tothe first shutter plate 5 a. The second shutter plate 5 b is initiallypivoted by the narrow portion 64 a of the first cam portion 64 on whichthere is engaged the first control projection 63 on the rotation wheel4. It should be noted that when the second shutter plate 5 b isinitially pivoted as above, the first bent portion 65 a of the secondcam portion 65 on the rotation wheel 4, on which the second controlprojection 66 of the second shutter plate 5 b is engaged, will not giveany force of rotation to the second control projection 66.

Further, when the rotation wheel 4 is rotated in a direction opposite tothe direction of arrow A, the guide projection 51 g engaged in the guiderecess 55 of the rotation wheel 4 is moved to the other end of the guiderecess 55 at the periphery of the rotation wheel 4 as shown in FIG. 18.As the first shutter plate 5 a is pivoted, the second shutter plate 5 bis pivoted about the second shaft 62 a of the first shutter plate 5 a inthe direction of arrow C in FIG. 17 in relation to the first shutterplate 5 a. Then, the first control projection 63 of the rotation wheel 4moves to the wider portion 64 b of the first cam portion 64 and will noact on the second shutter plate 5 b any more. Instead, the secondcontrol projection 66 of the second shutter plate 5 b is moved from thefirst bent portion 65 a to the second bent portion 65 b to pivot thesecond shutter plate 5 b in the direction of arrow C. Thus, the firstand second openings 24 and 44 are uncovered to expose the optical disk 3in the rotation wheel 4 to outside in a range between the inner andouter radii of the optical disk 3 as shown in FIG. 18.

Note here that the cartridge body 2 has provided therein a lockingmechanism 71 which locks the rotation wheel 4 against rotation, therebykeeping the first and second openings 24 and 44 covered with the shutterplates 5 a and 5 b as shown in FIGS. 17 and 18. More specifically, thelocking mechanism 71 includes a locking member 72 which locks therotation wheel 4, as shown in FIGS. 17, 18 and 19. The locking member 72includes a base portion 73 having formed therein a shaft hole 75 throughwhich there is passed a shaft 74 formed on the inner surface of thelower shell 7. Also, the base portion 73 has formed thereon a lockingportion 76 which locks the rotation wheel 4 against rotation, anunlocking piece 77 which is pressed by an insertion guide pin 100 alsoworking as an unlocking pin at the disk recorder and/or player, apivoting limiting piece 78 which limits pivoting of the base portion 73,and an engagement piece 79 on which the forcing member is engaged at oneend thereof. The locking member 72 is disposed near the insertion guiderecess 25 b at the side of the alignment hole 26 b formed on the rearside of the lower shell 7. The locking member 72 is installed to thelower shell 7 with the shaft 74 on the lower shell 7 being passedthrough the shaft hole 75.

Note that also when the locking member 72 is installed to the lowershell 7, the free end of the shaft 74 projects from the base portion 73.The projecting free end of the shaft 74 is engaged in the bearingportion 86 formed on the upper shell 6 to prevent the locking member 72from being disengaged from the shaft 74 even if a dropping shock or thelike is applied, namely, reinforce the shaft 74.

As shown in FIG. 19, the locking member 72 has the locking portion 76thereof directed inwardly, and the unlocking piece 77 thereof moved intothe insertion guide recess 25 b through a relief hole 80 formed in arising wall of the insertion guide recess 25 b. Also, the pivotinglimiting piece 78 abuts the boss 22 contiguous to the rising wall tolimit pivoting of the locking member 72.

Further, near the shaft 74 to which the locking member 72 is installed,there is formed a fixing pin 83 to which there is installed a forcingmember 82 such as a torsion helical spring or the like to force thelocking member 72 in one direction. The fixing pin 83 has a coil portionof the forcing member 82 wound thereon. The forcing member 82 installedon the fixing pin 83 is engaged at one arm portion thereof on the boss22, and at the other end on an engagement piece 79 of the lockingmember, thereby forcing the locking member 72 in a locking direction ofarrow D in FIG. 17 so that the unlocking piece 77 will be positioned atthe open end of the insertion guide recess 25 b.

The locking portion 76 of the base portion 73 is positioned slightlyinwardly of the periphery of the rotation wheel 4. The rotation wheel 4has formed therein in a position a little inner than the peripherythereof a locking recess 84 in which there is engaged the lockingportion 76 projecting from the base portion 73. The locking recess 84has an engagement concavity 85 formed therein. The engagement concavity85 is formed to have a vertical wall at the upstream side thereof.Therefore, when the rotation wheel 4 is rotated in the directionopposite to the direction of arrow A in FIG. 17, the locking portion 76will positively be engaged in the locking recess 84 with the verticalwall of the latter being placed to face the vertical surface of thelocking portion 76. The locking portion 76 is engaged in the engagementconcavity 85 to lock the rotation wheel 4 against rotation. As shown inFIG. 20, the locking recess 84 is formed below the taper portion 42formed along the base portion of the annular projection 43 on the sideof the rotation wheel 4 on which the optical disk 3 is to be received.The taper portion 42 is to support the peripheral edge of the opticaldisk 3 as having previously been described. The locking recess 84 isformed not deeper than necessary.

Note that the locking member 72 is formed from a synthetic resinsuperior in sliding performance, such as polyacetal resin, for example,to have a lower friction resistance against the lower shell 7 and shaft74.

Covering the first and second openings 24 and 44 with the shutter plates5 a and 5 b will be described below with reference to FIG. 17. Thelocking member 72 is forced by the forcing member 82 to turn about theshaft 74 in the direction of arrow D in FIG. 17. At this time, thelocking portion 76 is engaged in the engagement concavity 85 in thelocking recess 84 formed in a position inner than the periphery of therotation wheel 4. Therefore, the locking portion 76 is blocked againstpivoting since it is engaged in the engagement concavity 85. Even if therotation wheel 4 is applied with a force of rotating the rotation wheel4 in the direction opposite to the direction of arrow D, the lockingportion 76 will be applied with a force acting in the direction of arrowD in FIG. 17 and under which it will go into the engagement concavity85, Therefore, the locking member 72 can positively lock the rotationwheel 4 against rotation.

Also, as shown in FIG. 21, the unlocking piece 77 is moved through therelief hole 80 toward the front open end in the insertion guide recess25 b, and gets ready for pressing the insertion guide pin 100 which isalso the unlocking pin of the disk recorder and/or player. Morespecifically, the bottom of the insertion guide recess 25 b is open atthe front side thereof. The unlocking piece 77 is further moved from anend face 87 of the bottom of the insertion guide recess 25 b toward thefront open end, and gets ready to press the insertion guide pin 100which is also the unlocking pin of the disk recorder and/or player.Since the unlocking piece 77 is thus moved into the insertion guiderecess 25 b, the disk recorder and/or player can be prevented from beingoperated incorrectly.

When the disk cartridge 1 is inserted into the disk recorder and/orplayer, the unlocking pin is introduced into the insertion guide recess25 b as shown in FIG. 22. When the insertion guide pin 100 also servingas the unlocking pin of the disk recorder and/or player is moved fromthe front open end into the insertion guide recess 25 b, it will firstpress the unlocking piece 77, and then abut the bottom end face 87 whichdefines a position where the insertion guide pin 100 is to be inserted.Also, the insertion guide pin 100 will be moved into the insertion guiderecess 25 a as well. The unlocking piece 77 is pressed by the insertionguide pin 100 until it will abut the end face 87 which defines theposition of the insertion guide pin 100. Then, the locking member 72 ispivoted about the shaft 74 in the direction opposite to the direction ofarrow D against the force of the forcing member 82 as shown in FIG. 17.Therefore, the locking portion 76 is disengaged from the engagementconcavity 85 in the locking recess 84, and is moved in the lockingrecess 84 in conjunction with the rotation of the rotation wheel 4.

On the assumption that as in FIG. 23, the disk recorder and/or playerhas an unlocking pin 88 whose width is W₁ and the insertion guide recess25 b has a width of W₂, W₁≧W₂/2. Thus, the insertion guide pin 100 canpositively press the unlocking piece 77.

The disk cartridge 1 constructed as having been described in theforegoing is in a state as shown in FIGS. 1, 2 and 17 before it isloaded into the disk recorder and/or player. More particularly, when thepair of shutter plates 5 a and 5 b is covering the first and secondopenings 24 and 44, the rotation wheel 4 is in a position to which ithas been forced by the forcing member 48 to rotate in the direction ofarrow D in FIG. 17 and the to-be-operated member 45 is positioned at onelateral edge of the first opening 24. As shown in FIG. 11, theengagement recess 45 c in the to-be-operated member 45 cooperates withthe engagement recess 50 formed, near the second opening 44, in therotation wheel 4 to prevent the first shutter plate 5 a from going up ordown. Further, the second lateral edge 51 b of the first shutter portion51 is in mesh with the taper portion of the first lateral edge 61 a ofthe second shutter portion 61 in one direction, while the tape portionof the third lateral edge 51 c of the first shutter portion 51 is inmesh with that of the second lateral edge 61 b of the second shutterportion 61 in a direction opposite to the one direction. That is, in thedisk cartridge 1, the shutter plates 5 a and 5 b are thus in mesh witheach other and not easily flexibly deformable and the shutter plate 5 ais prevented from going up, whereby dust or the like is prevented frominvading the cartridge body 2.

At this time, the guide projection 5 g of the shutter plate 5 a ispositioned at one end, near the center, of the guide recess 55 in therotation wheel 4. Also, the first control projection 63 is engaged inthe narrow portion 64 a of the first cam portion 64 of the secondshutter plate 5 b. Further, the second control projection 66 on thesecond shutter plate 5 b is engaged in the first bent portion 65 a ofthe second cam portion 65 on the rotation wheel 4. Thus, in the diskcartridge 1, the first opening 243 of the lower shell 7 is closed asshown in FIG. 2. Also, even if the first shutter plate 5 a is pressed,the limiting projection 51 h of the first shutter plate 5 a will notabut the area at the inner radius of the optical disk 3, where noinformation signals are recorded, and the first shutter portion 51 willnot touch the signal recording area of the optical disk 3, so the signalrecording area can be prevented from being damaged.

Also, when the shutter plates 5 a and 5 b are covering the first andsecond openings 24 and 44, the rotation wheel 4 is lifted by the lifter14 on the upper shell 6 toward the lower shell 7 so that the projection27 formed along the peripheral edge of the first opening 24 will beengaged in the recess 51 f in the first shutter portion 51, whereby dustor the like is prevented from invading the cartridge body 2.

The locking mechanism 71 will be illustrated and described herebelow. Asshown in FIG. 17, the locking member 72 is forced by the forcing member82 to turn about the shaft 74 in the direction of arrow D in FIG. 17. Atthis time, the locking portion 76 is engaged in the engagement concavity85 in the locking recess 84. Therefore, as the locking portion 76 isthus engaged in the engagement concavity 85, the rotation wheel 4 isinhibited from rotating. If a force of forcibly rotating the rotationwheel 4 is applied in the direction opposite to the direction of arrowD, a force directed in the direction of arrow D in FIG. 17 is applied tothe locking portion 76 which will thus be moved into the engagementconcavity 85. Therefore, the locking member 72 can positively lock therotation wheel 4 against rotation.

Also, the unlocking piece 77 is moved toward the front open end in theinsertion guide recess 25 b through the relief hole 80 and gets readyfor pressing the insertion guide pin 100 also serving as the unlockingpin of the disk recorder and/or player as shown in FIG. 21. Morespecifically, the bottom of the insertion guide recess 25 b is open atthe front side thereof. The unlocking piece 77 is further moved from theend face 87 of the bottom of the insertion guide recess 25 b toward thefront open end, and gets ready for pressing the insertion guide pin 100also serving as the unlocking pin of the disk recorder and/or player.

The disk cartridge 1 having been described in the foregoing is insertedfirst at the generally circular front side thereof into the diskrecorder and/or player. When the disk cartridge 1 is inserted into thedisk recorder and/or player, a pair of insertion guide pins 100 formedon the latter is inserted into the disk cartridge 1. Since the insertionguide recesses 25 a and 25 b are formed widest at the front open end asshown in FIG. 7, the disk cartridge 1 can positively be guided to aspecific position on the cartridge mount. Also, when the width, at theinnermost portion, of the insertion guide recesses 25 a and 25 b isgenerally as the same as the thickness of the insertion guide pin, theinsertion guide pins 100 can accurately guide the disk cartridge 1 tothe specific position on the cartridge mount in the disk recorder and/orplayer.

When the disk cartridge 1 is placed on the cartridge mount in therecorder and/or player as shown in FIG. 24, the insertion guide pins 100are engaged in the location hole 26 a and alignment hole 26 b,respectively. The location hole 26 a is a reference hole for loading thedisk cartridge 1, and alignment hole 26 b is an adjustment hole. Wheninserting the disk cartridge 1 into the disk recorder and/or player, theunlocking piece 77 of the locking member 72 has to be pressed againstthe force of the forcing member 82. On this account, the unlocking piece77 is provided in the insertion guide recess 25 b at the alignment hole26 b for enabling more accurate positioning of the disk cartridge 1 onthe cartridge mount.

As the disk cartridge 1 is placed on the cartridge mount, the unlockingpin as the insertion guide pin 100 is moved into the insertion guiderecess 25 b through the front open end. It will first press theunlocking piece 77, and then abut the bottom end face 87. The unlockingpiece 77 is pressed by the unlocking pin 88 until the unlocking pin 88abuts the end face 87. Then, the locking member 72 is turned about theshaft 74 against the force of the forcing member 82 in the directionopposite to the direction of arrow D as shown in FIG. 17. Therefore, thelocking portion 76 is disengaged from the engagement concavity 85 in thelocking recess 84, and the rotation wheel 4 gets ready for rotation.

When the disk cartridge 1 is placed on the cartridge mount in the diskrecorder and/or player, the rotation wheel 4 is rotated by theto-be-operated member 45 against the force of the forcing member 48 inthe direction opposite to the direction of arrow A, and then the firstshutter plate 5 a having the guide projection 51 g thereof engaged inthe guide recess 55 in the rotation guide 4 is pivoted about the firstshaft 52 on the upper shell 6 in the direction of arrow B in FIG. 17. Asthe first shutter plate 5 a is thus pivoted, the second shutter plate 5b is pivoted about the second shaft 62 a on the first shutter plate 5 ain relation to the first shutter plate 5 a in the direction of arrow Cin FIG. 17. The second shutter plate 5 b is initially pivoted by thenarrow portion 64 a of the first cam portion 64 on which the firstcontrol projection 63 on the rotation wheel 4 is engaged. It should benoted that when the second shutter plate 5 b is initially pivoted asabove, the first bent portion 65 a of the second cam portion 65 on therotation wheel 4 on which the second control projection 66 on the secondshutter plate 5 b is engaged will not act in any way.

Further, as the rotation wheel 4 is rotated in the direction opposite tothe direction of arrow A in FIG. 18, the guide projection 51 g engagedin the guide recess 55 in the rotation wheel 4 is moved to the other endof the guide recess 55 along the periphery of the rotation wheel 4. Asthe fist shutter plate 5 a is pivoted, the second shutter plate 5 b ispivoted about the second shaft 62 a on the first shutter plate 5 a inrelation to the first shutter plate 5 a in the direction of arrow B inFIG. 18. Then, the first control projection 63 on the rotation wheel 4moves to the wide portion 64 b of the first cam portion 64 and will notact on the second shutter plate 5 b any more. Instead, the secondcontrol projection 66 on the second shutter plate 5 b moves from thefirst bent portion 65 a to the second bent portion 65 b to pivot thesecond shutter plate 5 b in the direction of arrow C in FIG. 18. Thus,the to-be-operated member 45 is positioned at the portion widened by thetaper portion 24 c of the first opening 24, the first and secondopenings 24 and 44 are uncovered as shown in FIG. 25, and thus theoptical disk 3 housed in the rotation wheel 4 is exposed to outside in arange between the inner and outer radii of the optical disk 3.

Then, the optical disk 3 housed rotatably in the rotation wheel 4 hasthe center hole 3 a thereof engaged on the disk table of the diskrotation driving mechanism in the disk recorder and/or player, is heldbetween the clamping plate 13 provided on the upper shell 6 and the disktable, and gets ready for rotation on the disk table.

For writing information signals to the optical disk 3 or readinginformation signals from the optical disk 3, the optical disk 3 isrotated on the disk table at CLV (constant linear velocity), CAV(constant angular velocity) or a combination of these velocities. Alongwith this operation, the optical pickup having moved into the first andsecond openings 24 and 44 writes information signals to the optical disk3 or reads information signals recorded on the optical disk 3 byemitting a light beam of about 400 nm in wavelength from a semiconductorlaser, condensing it by an objective lens, and irradiating it onto thesignal recording surface of the optical disk 3, and detecting a returnlight from the signal recording surface.

Note that when the disk cartridge 1 is ejected from the disk recorderand/or player, the rotation wheel 4 is forced by the forcing member 48to rotate in the direction of arrow D in FIG. 18, and returns from thestate in FIG. 18 to the state in FIG. 17. Then, the locking portion 76of the locking member 72 is moved in the locking recess 84 and engagedin the engagement concavity 85, and the first and second openings 24 and44 are thus covered again.

In the foregoing, the present invention has been described concerningthe small disk cartridge 1 as an embodiment thereof. However, thepresent invention is not limited to this embodiment but may be appliedto the disk cartridge of the standard size as disposed in theaforementioned Japanese Unexamined Patent Application Publication.

In the foregoing, the present invention has been described in detailconcerning certain preferred embodiments thereof as examples withreference to the accompanying drawings. However, it should be understoodby those ordinarily skilled in the art that the present invention is notlimited to the embodiments but can be modified in various manners,constructed alternatively or embodied in various other forms withoutdeparting from the scope and spirit thereof as set forth and defined inthe appended claims.

1. A disk cartridge, comprising: a cartridge body including a lowershell having formed therein a first opening for write and/or read and anupper shell butt-joined to the lower shell; a rotation wheel housedrotatably in the cartridge body and which houses a disk and has formedtherein a second opening corresponding to the fist opening and throughwhich the housed disk is exposed to outside; and a shutter mechanismprovided between the lower shell and rotation wheel and which operateswith the rotation of the rotation wheel to uncover the first and secondopenings when the latter are coincide with each other; and a lockingmechanism including a shaft portion installed pivotably to any one ofthe shells, a locking portion engaged in an engagement concavity in therotation wheel to lock the rotation wheel in a position where theshutter mechanism covers the first opening, and an unlocking portionwhich cancels the engagement of the locking portion in the engagementconcavity, the cartridge body having formed therein an insertion guiderecess open at the side of the cartridge body, at which the latter isfirst inserted into a disk recorder and/or player; and the lockingportion having an unlocking piece which is opposite to the insertionguide recess.
 2. The disk cartridge according to claim 1, wherein theengagement concavity in the rotation wheel is formed inside theperipheral edge of the rotation wheel.
 3. The disk cartridge accordingto claim 1, wherein: the lower shell has formed therein a pair of theinsertion guide recesses separately from each other, one of theinsertion guide recesses being extended by a location hole while theother insertion guide recess is extended by an alignment hole; and theunlocking piece of the locking member is projected to outside from thealignment hole-side insertion guide recess.
 4. The disk cartridgeaccording to claim 1, wherein a taper portion which supports theperipheral edge of the disk is formed along one side of the rotationwheel and an engagement concavity in which the locking portion is to beengaged is formed in the other side formed thick and on which a rib isformed.
 5. The disk cartridge according to claim 1, wherein the lockingmember is supported pivotably on a shaft formed on the lower shell, theshaft being formed higher than the locking member.
 6. The disk cartridgeaccording to claim 1, wherein the insertion guide recess has a limitingportion an unlocking pin included in the disk recorder and/or playerabuts and has formed therein a relief hole in which the unlocking piecepressed by the unlocking pin will retreat.
 7. The disk cartridgeaccording to claim 1, wherein the insertion guide recess is formed widerat the open end thereof.
 8. The disk cartridge according to claim 1,wherein on the assumption that the unlocking pin of the disk recorderand/or player has a width W₁ and the insertion guide recess has a widthW₂, W₁≧W₁/2.
 9. The disk cartridge according to claim 1, wherein thelocking member is formed from a resin superior in sliding performance.